1. Field of the Invention
The present invention relates to an ink jet recording apparatus for recording by discharging ink from recording means to a recording medium, and an ink tank used for the ink jet recording apparatus. More particularly, the invention relates to an ink jet recording apparatus for recording in plural colors, and an ink tank used for such ink jet recording apparatus.
2. Related Background Art
A recording apparatus provided with the function of a printer, copying machine, facsimile or the like or a recording apparatus used as an output equipment for a complex machine including a computer, a wordprocessor, and the like or a work station, is structured to record images (including characters, symbols, and others) on a recording material (recording medium) such as a sheet or a thin plastic board (OHP or the like). Such recording apparatuses can be divided into those of an ink jet type, wire-dot type, thermo-sensitive type, thermo-transfer type, laser beam type, and others according to the recording type of recording means adopted by each of them.
In a recording apparatus of a serial type, which adopts a recording method where its main scan is performed in the direction intersecting the feeding direction of a recording material (that is, the subscanning direction), images (including characters, symbols, and others) are recorded by recording means mounted on a carriage movable along the recording material (that is, the main scanning) after a recording material is set at a given recording position. Then, after the completion of recording one line of an image, the sheet is fed (subscanned) for a given amount in order to record the next line of the image (main scanning). By repeating this operation, the image is recorded in a desired area of the recording material.
On the other hand, in a recording apparatus of a line type whose recording is executed only by subscanning where the recording material is fed, a recording material is set at a given recording position, and then, a sheet feeding is performed for a given amount (in a pitch feeding mode) while one line is recorded continuously altogether; hence recording images on the entire area of the recording material.
Of these types, those of an ink jet type (ink jet recording apparatuses) are to record by discharging ink from recording means (recording head) to a recording material to make it possible to provide compact recording means with ease for recording highly precise images at high speeds. With this type, it is also possible to record on an ordinary sheet without any particular treatments, hence at a lower running cost. Moreover, being non-impact, this type makes less noises besides a remarkable advantage that many different colors of ink can be used for recording images in colors without difficulty. Particularly, in a recording apparatus of a line type using a line type recording means in which many numbers of discharge ports are arranged in the width direction of a sheet, it is possible to implement the provision of a higher speed recording.
Especially, recording means (recording head) of an ink jet type which discharges ink by utilizing thermal energy can be easily processed to provide the recording means in which liquid paths (discharge ports) are arranged in a high density by the film formation of electrothermal transducing elements, electrodes, walls of liquid paths, and a ceiling on a base board through etching, deposition, sputtering, and some other semiconductor processing steps. This contributes significantly to attaining the manufacture of more compact recording means.
Also, with the utilization of such known advantages of the IC technologies and micro machining techniques, it becomes easier to elongate the recording means or effectuate its surfacing (two-dimensional arrangement) as well as to make the recording means fully multiple and highly densified when it is assembled.
This ink jet recording apparatus comprises recording means formed by discharge port groups, ink droplet generating mechanism, and others; ink paths for conducting ink to the recording means; and ink retaining means (ink tank) for retaining ink to be supplied to the recording means through the ink paths.
An ink jet type of the kind is often adopted for use of a recording apparatus whose recording mode is not only such as using a single type of ink, but also, using plural kinds of ink having different densities (concentrations) and colors so that tonal images or color images can be recorded by conducting such kinds of ink to given discharge ports for discharging as required. Now, given below, the description will be made of a structural example (type) representing the apparatus for which plural kinds of ink are used.
As a first type, there can be named the one in which recording means, ink paths, and ink tank are integrated as a unit per ink to be used, and installed on one base member (a carriage of a serial recording apparatus, for example).
Then, as a second type, there can be named the one in which a unit, which is provided with the recording means, ink paths, and ink tank integrally formed, is installed on a carriage for discharging three colors--yellow, magenta, and cyan (hereinafter abbreviated as Y, M, and C)--such as disclosed in Japanese Patent Laid-Open Application No. 63-87242. In this type, while a recording is performed in colors, Y, M, and C are overlaid for printing in black as required.
Also, as a third type, there can be named the one in which recording means, having the Y, M, and C units of the second type described above, is fixed to a carriage, but an arrangement is made so that the ink tank can be attached to or detached from the carriage instead of the recording means as disclosed in Japanese Patent Publication No. 1-12675.
In accordance with the conventional examples described above, however, there are disadvantages that even when only a specific kind of ink is used, the amount of usable ink is kept at the same level as that of ink used at the time of entire ink tanks being installed or that even if the larger amount of ink can be arranged for supplying a specific color, it costs inevitably more to make such specific provision possible.
Here, more precisely, to begin with the first type described above. Since a unit is provided for each ink in this type, it is possible to increase the capacity of a tank for a specific ink, black, for example. However, if a particular unit should be made larger than the other units to meet this requirement, there is a need for a space arranged to be large enough in the height direction just to match one tank whose capacity is increased, because the plural units are arranged in line for use. Accordingly, an ink jet recording apparatus should be made larger in size to adopt the first type described above.
Also, in the second type described above, each ink of Y, M, and C must be overlaid for printing in black, thus requiring a considerable amount of ink for each color. In this case, therefore, if its use is often confined to printing in black, it should be more advantageous to arrange the selective installation of a unit which is provided integrally with recording means, ink paths, and ink tank formed for the dedicated use of Bk ink. The reason is that the amount of ink for the dedicated Bk unit is substantially equal to the combined amount of three ink colors of Y, M, and C units, and that by use of one specific unit, more recording is possible, leading to the enhanced volumetric efficiency.
However, this brings about disadvantages in terms of cost performance because recording means should also be made exchangeable just for using Bk and other colors separately, while the recording means itself is already an expensive component of an ink jet recording apparatus.
Also, in regard to the printing in Bk while executing color recording, if an integrated unit of four colors, Y, M, C, and Bk, is adopted to execute printing only by use of Bk ink instead of the mode in which printing in black is performed by overlaying Y, M, and C ink, the overall efficiency of ink usage or the volumetric efficiency is still lowered eventually.
Further, in the third type described above, the ink tanks are arranged to be exchangeable. It is possible to use ink tanks having different capacities with ease at a lower cost. However, if a large ink tank should be installed, the recording apparatus should also be arranged in a larger size accordingly. In this aspect, the third one is the same as the first type described above. Also, there may be encountered a drawback that if only a specific ink tank is installed, the remaining ink having its specific properties may be dried and solidified in the ink paths where the other ink tank should be installed for using ink of different properties.